Q will go only G goes

[XiaoruiD273]

I have a hard time to understand premises like this, can anybody explain this to me well? Thanks!

Q will go only G goes.

It must be true that...

-Q ➡️ - G

Q ➡️ G

I chose first answer but it turned out second answer is the right one. I think my problem is to understand what it means "unless".